
where \( u \in \mathbb {R}^{N} \)  and \( u - (x_1 +x_2 ) = \mathbf {0}\) .
Note that \(F(u)\)  is exactly identical to GSSD problem
{see Equation (20) in [1]}}.
Adopting Theorem 1 and Corollary 2 in [1]},
it can be shown that: when
\(0 \le a_0 < \frac{1}{K_0\lambda _0},\) 
